Preparation of aliphatic dicarboxylic acids



United States Patent 2,938,051 PREPARATION OF AklPgAgTlC DICARBOXYLIC Martin W. Farrar, Webster Groves, Mo., assignor to Monsanto Chemical Company,'St. Louis, Mo., a corporation of Delaware No Drawing. Filed Nov. 1, 1956, Ser. No. 619,692

5 Claims. or. 260-531) This invention relates to the preparation of aliphatic dicarboxylic acids and more specifically pertains to the preparation of aliphatic dicarboxylic acids by the reaction between an alicyclic alcohol or ketone with an alkali metal or alkaline earth'metal hypohalite.

Various processes have been proposed for the preparation of aliphatic dicarboxylic acids involving the oxidation of alicyclic alcohols or alicyclic ketones. Briefly suchproposed processes include the oxidation of a cycloaliphatic hydrocarbon with air or oxygen, the partial oxidation of a cycloealiphatic hydrocarbon to a mixture containing an alicyclic ketone and an alicyclicalcohol followed by the nitric acid oxidation of the mixture of the alcohol and ketone to the desired carboxylic acidand the oxidation of a cyclo-aliphatic ketone or cycle-,- aliphatic alcohol with nitric acid to the desiredv aliphatic dicarboxylic acid. All of the proposed processes have procedural drawbacks. The nitric acid oxidations are very sensitive and unless very carefully controlled become substantially spontaneous and explosive in nature. The air or oxygen oxidations require special equipment since they are most efliciently carried out at super-atmospheric pressures. The nitric acid oxidations also involve recovery of the by-product oxides of nitrogen to make most efiicient use of the starting materials.

An alternate route to the preparation of aliphatic dicarboxylic acids from cyclo-aliphatic ketones and alcohols has been discovered. The alicyclic ketones and alcohols involved in this process are those havingthe carbonyl carbon as a member of the alicyclic ring or.- having the hydroxyl group of the alcohol attached to a carbon which is a member of the alicyclic ring. 7 This. process involves the oxidation of the cyclo-aliphatic alcohol or ketone with an alkali metal or alkaline earth metal hypohalite at a temperature of from about C. to about 100 C. when the process is carried out 'at atmospheric pressure. Temperatures above 100 C. at atmospheric pressure will cause a too rapid decomposition of the hypohalite and thus reduce the efiiciency of the oxidation process, buttemperaturesabove' 100 C. can be employed when the process is carried out at super-atmospheric 'pressures. In general, the use of a hypohalite as an oxidizing agent is not-new to the art and the temperature conditions required for eificient use of an alkali metal hypohalite as the oxidizing agent are well understood by those skilled in the art. However, the novelty in the process of this invention lies in the fact that an alkali metal or alkaline earth metal hypohalite can be employed to oxidize an alicyclic ketone containing 6 to 8 carbon atoms and containing as a ring member the carbonyl carbon atom or an alicyclic alcohol whose'hydroxyl group is attached to a'ring carbon atom which contains from 6 to 8 carbon atoms to produce a dicarboxylic acid having the same number of carbon atoms as the starting ketone or alcohol. Representative ketones and alcohols useful in the process of this invention include: cyclohexanone, dimethyl cyclohexanone, cycloheptanone, cyclohexanol, gem. dimethyl cyclohex e CC anol, 3-nitro cyclohexanol, cyclohexenol A 3,5-dimethyl cyclohexanol and cycloheptanol.

. The process of this invention is carried out by adding the alicyclic alcohol or ketone to an aqueous solution. of the alkali metal or alkaline earth metal hypohalite. Preferably the aqueous solution of the hypohalite con- ;tains' free alkali metal hydroxide in an amount of from I about 5% to about 25% by weight of the aqueous solutaining more than 15% by'weight of the hypohalite, that is, up to to by weight of the alkali metal'lorr -alkaline earth metal hypohalite, can be used-quite efilr i ciently. Aqueous solutions containing more than 30%.; by weight alkali metal hypohalite can be used since" the; oxidation reaction of the process of this invention consumes at least 3 equivalents of the alkali metal or alkaline earth metal hypohalite 'per mole of alicyclic ketone or alcohol oxidized to the dicarboxylic acid and the use of such concentrated aqueous solutions providing such quan titles of the alkalimetal and alkaline earth metal hypohalites, when available, will provide adequate liquid diluent for the efficient removal of the heat of reaction.

understood that where less' than 3 equivalents of hypohalite per. mole of alkali ketone are employed the elliciency of oxidation of the ketone will be low and unox- Y idized ketone will remain in the reaction mixture. .But, for the most efiicient use of the reactants it is preferred;

1*. that the reactants be combined in a ratio of 3 or more equivalents of hypohalite per mole of ketone and at least 4 moles of alkali metal hypohalite per mole of alicyclic alcohol.

As the preferred alkali metal and alkaline earth metal.

. hypohalite reactant, there can be employed in the process of this invention; sodium hypochlorite, potassium hypo chlorite, sodium hypobromite, potassium hypobromite,, sodium hypoiodite, potassium hypoiodite, calcium hypochlorite, calcium hypobromite, calcium hypoiodite, barium.

thypochlorite, barium hypobromite, barium hypoiodite.

Other of the alkali metal hypohalites, such as the lithium, rubidium and cesium, as well as other of the alkaline earth metal hypohalites, may be employed. However, their availability and cost do not lend to. the preferred.

i status of sodium, potassium, calcium and barium.

hypohalites.

The following examples will serve further to illustrate this invention without, however, limiting the same. The term parts is employed in these examples to indicate: parts by weight.

- resulting mixture is'stirred for, about 2 hoursand held;

at about room temperature, that is, 25 to 27 C. Thereafter the reaction mixture is acidified with an amount of concentrated hydrochloric acid (37% HCl) in excess of the theoretical amount required to convert all of the sodium adipate to adipic acid, pH of reaction medium Example! 7 v aos'apbt 3.. about i, whereupon adipic acid precipitated. The resulting solution is stirred and cooled to about C. and then filtered. The recovered adipic acid is washed with ice water and dried at 75- to 80 C. In this manner there is recovered adipic acid having a melting point of 1 50 to 152 C. in a. yield representing 82% of the theoretical yield.

- Example 11 The process described in Example I is repeated except that an equivalent amount of sodium hypochlorite is employed instead of sodium hypobromite. The quality of the adipic acid recovered is substantially the same as tiiat'recovered from the process of Example I andthe yield of adipic acid is in excess of 80% of the theoretical yield,

Example Ill i-The process of Example I is repeated except that an equivalent amount ofcalcium hypochlorite is employed in the place of sodium hypob'rom'ite. By this process there is obtained an excellent quality adipic acid comparable to that produced by the process of Example I.

Example IV Adipic acid is produced by oxidizing cyclohexanol by the addition thereof to an aqueous solution of sodium hypobromite at a temperature of about 40 C. After all the sodium hypobromite has reacted, a ratio of hypobromite to cyclohexanol of about 4 equivalents per mole of cyclohexanol being used, the resulting reaction mixture is acidified with concentrated hydrochloric acid, the acidic solution cooled and adipic acid is recovered;

In this manner, yields of adipic acid of80% and above;

may be obtained.

' Example V 2,4-dimethyl adipic acid is prepared by oxidizing 3,5- dimethyl cyclohexanol by the addition thereof to an aqueous solution containing about 28 to 30% sodium hypobromite at a temperature at 20 to 25 C. Upon acidification and cooling of the resulting reaction mixture anv excellent yield of high quality 2,4-dimethyl adipic acid is recovered.

. As mentioned above, the uniqueness of the processof this invention is the fact that a dicarboxylic acid can be obtained from an alcohol or ketone containing thesarne number of carbon atoms as the ketone or alcohol emplayed as" a starting material. According to the prior art, hypohalites have been employed in the preparation of dicarboxylic acids by the oxidation of methyl ketones having the formula wherein R is a cyclic group. Ring cleavage occurs between the carbon atom to which the carbonyl group is attached and a carbon immediately adjacent thereto. However, in such a process the methyl groupis c'orn pletely oxidized and is replaced by a hydroxyl group. However, this is not the case in' the process of this in vention. As illustrated the carbon and hydrogen group directly adjacent to the carbonyl carbon atom is not destroyed but becomes a carboxylic acid group. so that a dicarboxylic acid of the same numer of carbon atoms as 4 modifications obvious to those skilled in the art may be employed without departing from the spirit and scope of this invention as defined in the appended claims.

What is claimed is: 1. In a process for the preparation of an aliphatic dicarboxylic acid containing 6 to 8 carbon atoms the step comprising reacting a member having the same number of carbon atoms as said acid and selected from the group consisting of monohyclroxy alicyclic alcohols having the hydroxy group attached to a carbon atom of the alicyclie ring and alicyclic ketones having only a single carbonyl group whose carbonyl carbon is a member of 1 the alicyclic ring, with an oxidizing agent selected from reacting in an aqueousmedium a member having the said number of carbon atoms as said acid and selected from the group consisting of monohydroxy alicyclic alcohols having the hydroxy group attached to a carbon atom of the alicyclic ring and alicyclic ketones having 1 carboxylic acid containing 6 to 8 carbon atoms which comprises reacting at .a temperature of from 0 C. to 100 CL in an aqueous medium a member selected from the groupconsisting of monohydroxy alicyclic alcohols having the hydroxy group attached to a carbon atom of -the alicyclic ring and alicyclic ketones having only a single carbonyl group whose carbonyl carbon is a part of the alicyclic ring, with at least 3 molecular proportions of an -oxidizing agent selected from the class consisting of alkali metal and alkaline earth metal hypohalite for each mole of alicy'clic reactant, acidifying the aqueous reaction mixture and recovering an aliphatic dicarboxylic acid having the same number of carbon atoms as said member.-

4. In a process for the preparation of adipic acid the step comprising reacting in an aqueous reaction medium at a temperature of from 0 C. to 100 C. cyclohexanonewith at least 3 molecular proportions of an alkali metal hypohalite for each molecular proportion of cyclohexanone.

' 5. The process for the preparation of adipic acid comprising adding cyclohexanone to an aqueous solution of sodium hypobromite at a temperature of about 20 C., maintaining the resulting mixture at a temperature of from 20 C. to 30 C, acidifying the resulting slurry with hydroehloric acid, cooling the acidic slurry to a 2,191,786 Aronow Feb. 21', 1 40 2,235,914 Drossbacli Juries, 1942 2,293,211 Cavariaugh s July 28, 1942' OTHER REFERENCES- teni er ture of from about 0 c. to about 10 C. and recovering adipic acid.

l References Cited in the file of this patent UNITED STATES PATENTS et aL: Chem. Rev., vol. 15 (1034), pp. 28 8 9. Gilman; Organic Chemistry, vol. I,- 2nd. ed. (1938), rr-

'Ephraimz. Inorganic Chemistry, 4th ed. (edited by Thorns et'a'l.) .1943, pp. 358-68. 

1. IN A PROCESS FOR THE PREPARATION OF AN ALIPHATIC DICARBOXYLIC ACID CONTAINING 6 TO 8 CARBON ATOMS THE STEP COMPRISING REACTING A MEMBER HAVING THE SAME NUMBER OF CARBON ATOMS AS SAID ACID AND SELECTED FROM THE GROUP CONSISTING OF MONOHYDROXY ALICYCLIC ALCOHOLS HAVING THE HYDROXY GROUP ATTACHED TO A CARBON ATOM OF THE ALICYCLIC RING AND ALICYCLIC KETONES HAVING ONLY A SINGLE CARBONYL GROUP WHOSE CARBONYL CARBON IS A MEMBER OR THE ALICYCLIC RING, WITH AN OXIDIZING AGENT SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL AND ALKALINE EARTH METAL HYPOHALITES. 